1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, a program, and a recording medium, and particularly, to an image filtering process.
2. Description of the Related Art
Various image filtering process techniques such as a filtering process for enhancing image quality or a filtering process for providing a special visual effect have been proposed. For example, a point image restoration process that restores an original image using a filter determined based on a point spread function (PSF) indicating an image deterioration characteristic due to aberration of an imaging lens or the like is known.
JP2009-206822A discloses an imaging apparatus for the purpose of improving a manufacturing tolerance to reduce manufacturing variation. The imaging apparatus includes an aberration control optical system and an image processing unit. In the aberration control optical system, a spherical aberration greatly occurs in a peripheral portion compared with the vicinity of the center of an optical axis. The image processing unit performs a restoration process of components degraded due to the spherical aberration, and retains the amount of noise increased by the image processing to be equal to or less than two times in a standard deviation. In this way, by intentionally generating spherical aberration at a position distant from the optical axis, a manufacturing tolerance of a lens is improved. Further, by restoring an MTF by image processing using a filter, a recovery process of the components degraded by the spherical aberration is performed.
Further, JP2010-147926A discloses an imaging apparatus that generates an image having an enlarged depth of field and an image having an arbitrary depth of field by image processing after imaging. In JP2010-147926A, in a case where a point spread function (PSF) is directly calculated with respect to all pixel positions in an original image, since a processing amount increases and a processing time becomes long, a technique for directly calculating a point spread function only with respect to representative pixel positions, and acquiring a point spread function relating to non-representative pixel positions by performing interpolation based on the point spread function relating to the representative pixel positions in the vicinity thereof is disclosed.